Thermal Resistance Sensor Classification

1. NTC thermistor sensor:
This type of sensor is a negative temperature coefficient sensor, that is, the sensor resistance decreases as the temperature increases.
2. PTC thermistor sensor:
This type of sensor is a positive temperature coefficient sensor, that is, the sensor resistance increases as the temperature increases.
Laser
A sensor that uses laser technology for measurement. It consists of a laser, a laser detector and a measuring circuit. The laser sensor is a new type of measuring instrument. Its advantages are that it can achieve non-contact long-distance measurement, fast speed, high accuracy, large range, strong resistance to light and electrical interference, etc.
When the laser sensor is working, the laser emitting diode first aims at the target and emits a laser pulse. After being reflected by the target, the laser scatters in all directions. Part of the scattered light returns to the sensor receiver, and is received by the optical system and imaged onto the avalanche photodiode. The avalanche photodiode is an optical sensor with an internal amplification function, so it can detect extremely weak light signals and convert them into corresponding electrical signals.
Non-contact long-distance measurement can be achieved by utilizing the high directivity, high monochromaticity and high brightness of the laser. Laser sensors are commonly used to measure physical quantities such as length (ZLS-Px), distance (LDM4x), vibration (ZLDS10X), speed (LDM30x), and orientation. They can also be used for flaw detection and monitoring of atmospheric pollutants.
Hall
Hall sensors are magnetic field sensors made based on the Hall effect, and are widely used in industrial automation technology, detection technology, and information processing. The Hall effect is a basic method for studying the performance of semiconductor materials. The Hall coefficient measured by the Hall effect experiment can determine important parameters such as the conductivity type, carrier concentration, and carrier mobility of semiconductor materials.
Hall sensors are divided into linear Hall sensors and switch Hall sensors.
1. The linear Hall sensor consists of a Hall element, a linear amplifier, and an emitter follower, and it outputs analog quantities.
2. The switch Hall sensor consists of a voltage regulator, a Hall element, a differential amplifier, a Schmitt trigger, and an output stage, and it outputs digital quantities.
The Hall voltage changes with the change of the magnetic field strength. The stronger the magnetic field, the higher the voltage, and the weaker the magnetic field, the lower the voltage. The Hall voltage value is very small, usually only a few millivolts, but after being amplified by the amplifier in the integrated circuit, the voltage can be amplified to a level sufficient to output a strong signal. If the Hall integrated circuit is to be used as a sensor, a mechanical method is required to change the magnetic field strength. The method shown in the figure below uses a rotating impeller as a switch to control the magnetic flux. When the impeller blades are in the air gap between the magnet and the Hall integrated circuit, the magnetic field deviates from the integrated chip and the Hall voltage disappears. In this way, the change in the output voltage of the Hall integrated circuit can indicate a certain position of the impeller drive shaft. Using this working principle, the Hall integrated circuit chip can be used as an ignition timing sensor. The Hall effect sensor is a passive sensor. It requires an external power supply to work. This feature enables it to detect low-speed operation.